1. Field of the Invention
The present invention relates to a radar system which includes an electronic circuit using a high electron mobility transistor, and is typically used as a vehicle-mounted radar.
2. Description of the Related Art
In the related art, there is known a radar system that measures the distance to a detection target based on a time after transmission of a wave till reception of the wave reflected from the detection target. There is also known a radar system that detects a relative velocity to the detection target using the Doppler effect. There is further provided a radar system further having a function of position detection by use of a frequency-modulated carrier wave. Such kind of radar systems have been typically used as a vehicle-mounted radar to measure the relative distance and relative velocity to an obstacle such as a preceding automobile or the like. Such radar systems including the vehicle-mounted radar are obliged to use a limited frequency band regulated by law, and generally using a microwave, a submillimeter wave, or a millimeter wave. In many cases, electronic circuits for such frequencies use a semiconductor device of compound semiconductor. In particular, such semiconductor device as what is called HEMT (high electron mobility transistor) having good high frequency characteristic is commonly used.
Japanese Patent Publication No. 10-62525 discloses a method for implementing failure detection for high frequency circuit components in a radar system outputting a frequency-modulated transmission wave. Japanese Patent Publication No. 2004-80865 discloses a method for implementing failure detection for semiconductor devices by measuring a temperature thereof. In the above-mentioned failure detection methods, failure of a circuit component is detected when there is a certain abnormality found in the circuit component in its ordinary operation. Namely, failure detection for the circuit component is implemented while the device is operated in its ordinary operating state.